This post is possibly not one for the squeamish, but lately I’ve become more aware of these bright little flies and given thought to the vital role they and their kind play in maintaining balance in our environment, so decided it was time to learn more about them. Yellow dung-flies are one of the most familiar and abundant flies here in the United Kingdom and indeed throughout much of the Northern Hemisphere. They are out and about from March to November and at their peak in the summer. Anyone that walks in the countryside, particularly in areas where there are large mammals will undoubtedly have seen them. They may look a little fearsome close up, but are harmless to us, they do not sting or bite people or other animals!

Common Yellow dung-fly or Golden dung-fly – Scathophaga stercoraria

Yellow -dung-fly male

As its common name suggests, the life of a Yellow dung-fly, particularly that of the males is centred on, yes you’ve guessed it … dung! They spend most of their lives either upon it, or looking for it. They favour cow pats, but are adaptable and will settle for the dung of other large mammals such as horses, deer or wild boar if that’s what’s available. Unsurprisingly here in Wales they mostly have to settle for that of sheep.

Male and female yellow dung-flies

Dung-flies belong to the Scathophagidae family of flies which are integral within the animal kingdom in the role of assisting in the process of the natural decomposition of dung in fields and grasslands.

Description: 5-11mm long. Average lifespan is 1-2 months. Sexually dimorphic, males are golden-yellow with orange-yellow fur on their front legs and are larger than the females. Females are generally duller in appearance, more of a green-brown colour and have no brightly coloured fur on their front legs.

Behaviour

Males and females are attracted to fresh dung by its scent and actually approach deposits flying into the wind. Males spend most of their time on the dung waiting for females to mate with and being predatory insects, sometimes feeding on other insects that visit the dung, such as blow flies. Females on the other hand spend most of their time foraging in vegetation and only visit dung to mate and subsequently deposit her eggs.

Reproduction

Rival male dive-bombing a mating pair

The male-female ratio of flies on a dung pat is typically heavily biased towards males. Often several males can be seen waiting for a female to arrive, so if and when one does, competition to mate is high: the smaller, outnumbered females don’t have much say in choosing their mate.

The act of copulation lasts 20 to 50 minutes during which the couple may be subject to aerial attacks from rival males attempting to dislodge the male. When the act is completed, the male attempts to guard the female from the attentions of other males, although both males and females often mate with several individuals.

Life-cycle

The adult dung-fly is mainly carnivorous, catching and eating smaller insects, but they also eat nectar. After mating females lay their eggs on the dung, where she selects small ‘hills’ on its surface, deliberately avoiding depressions and sharper pointed areas. This strategy is aimed at preventing desiccation and drowning thus giving eggs and offspring the greatest chance of survival. Depending on ambient temperature eggs hatch into larvae after 1-2 days. Larvae burrow quickly into the dung for their protection and proceed to feed on it; they also predate on other insect larvae also living in the dung. They grow rapidly and after 10-20 days the larvae burrow into the soil around and beneath the dung where they pupate.

Environmental influences

The Yellow dung-fly has a short life cycle, a factors that has made them of interest to scientists, who have been able to study not only the insects themselves but also the effects various environmental factors has on them. For example:

The viability of a clutch of eggs depends strongly on the environment. In warmer climates a sharp drop in population occurs during the summer when temperatures increase to 28° or above. This does not happen in places with a colder climate such as Iceland, Finland and the north of Britain, nor at higher elevations.

The health of juvenile dung flies is in turn affected by the quality of the dung they inhabit, factors such as water content, nutritional quality, the presence of parasites & drugs and chemicals given to the animal that excreted it may all contribute.

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11 thoughts on “The life of a Yellow Dung-fly”

Thank you and yes, these photos were taken with a zoom lens. I have been known to get down to ground level to get better close-ups, but that often ‘spooks’ the insects and I end up with a lot of pics of just dung! My guess is that as chemicals affect bees, then they must also affect other insects in some way or another. Farmed animals are regularly dosed with all kinds of stuff to keep them healthy, some to kill parasites, so presumably some of this is passed out in their poo. I suppose the only consolation is that this has been happening for years and there seem to be plenty of dung flies around, at least for now.

Good photos! On a zoom? Was just thinking myself of the amazing insect life that goes on and to try and investigate it more! Really informative and I think we know very little about the consequences on insects of our use of so many chemicals on domestic creatures. And the fate of vultures in India has been awful with cows being given certain medication. Insects are crucial too to a healthy ecosystem. I only partially cobweb but always leave some and the spiders as I hope they help with keeping the flies and Mosquitos down !

That is so true Pat, to quote Shakespeare: “There are more things in heaven and earth, Horatio,Than are dreamt of in our philosophy.” I’m really sorry to hear your sad news, which must be particularly hard as he was your youngest brother too. My heartfelt best wishes go to you and your family, Theresa

I’ve never heard of a dung fly or seen one before. Interesting! So many wonders in the natural world, each serving a purpose.
(Sorry I haven’t been around, but my youngest brother passed from cancer. Have been focused on trips to be near him since mid-June.)

They certainly do Suzanne and they are seriously under-appreciated! I find them fascinating but before researching for this post I hadn’t really considered the impact we may be having on our natural waste-disposers through treating domesticated animals with drugs and chemicals.

“The male-female ratio of flies on a dung pat is typically heavily biased towards males and competition is high: the smaller females don’t have much say in choosing their mate.” – Does this mean there are many more males and they gang up on the smaller females or that there are many more females and they have a lack of partners?

Sorry, that does sound ambiguous; I meant that there are more males than females. Often several males can be seen waiting hopefully on a dung pat, then when a female arrives she’s pounced upon almost immediately without ceremony or preamble. But then she is likely to mate with more than one male anyway, apparently all in the interest of ensuring she secures the most compatible sperm for strong healthy offspring, so in that respect she does get choice, even if she’s not aware of it! Hope that makes more sense.